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Maternal age, fertility treatment, and the temporal effect on the twinning rate in Cardiff and Vale of Glamorgan (1980–2004)
  1. H Faisel1,
  2. Z Roberts2,
  3. P Lindsay1
  1. 1Cardiff and Vale NHS Trust, Cardiff, UK
  2. 2Epidemiology Department, Cardiff University, Cardoff, UK

Abstract

Objective Estimate the influence of maternal age, fertility treatment and period of delivery (temporal effect) on twin maternities

UnadjustedAdjusted
Period:No (twin/total)OR95% CIp ValueOR95% CIp Value
1980–1984*284/2770211
1985–1989**139/128901.050.8, 1.20.621.030.84, 1.260.7
1990–1994425/305301.31.1, 1.5< 0.00011.31.1, 1.50.001
1995–1999484/284971.61.4, 1.9< 0.00011.51.3, 1.7< 0.0001
2000–2004425/247771.61.4, 1.9< 0.00011.71.4, 1.9< 0.0001
Age group
25–29*507/3878811
15–1960/110260.40.3, 0.5< 0.00010.40.3, 0.6< 0.0001
20–24332/299330.80.7, 0.90.0190.90.8, 1.060.3
30–34557/304811.41.2, 1.5< 0.00011.21.08, 1.30.001
35–39267/121071.71.4, 1.9< 0.00011.31.1, 1.5< 0.0001
40–45 34/20611.20.8, 1.70.180.90.6, 1.30.7
Fertility treatment
No1440/11926811
Yes317/51285.44.7, 6.1< 0.00014.84.2, 5.5<0.0001
  • * Reference group against which OR is expressed.

  • ** 50% of data are missing for this period.

  • Methods The authors performed an age period cohort analysis. A logistic regression model was used to assess the independent effect of each factor on twinning.

    Results The following table summaries the odds of twinning by maternity periods, maternal age and fertility treatment:

    Conclusion Our analysis confirms the importance of maternal age and fertility treatments on twin maternities. It also suggests a temporal effect, which may reflect recent changes in the environment surrounding pregnancy (nurture).

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